Gas concentrator with removable cartridge adsorbent beds

ABSTRACT

A portable oxygen concentrator designed for medical use where the sieve beds, adsorbers, are designed to be replaced by a patient. The concentrator is designed so that the beds are at least partially exposed to the outside of the system and can be easily released by a simple user-friendly mechanism. Replacement beds may be installed easily by patients, and all gas seals will function properly after installation.

RELATED APPLICATIONS

Not Applicable

FEDERALLY SPONSORED RESEARCH

Not Applicable

SEQUENCE LISTING

Not Applicable

BACKGROUND OF THE INVENTION

The invention generally relates to gas concentrators, and moreparticularly relates to medical oxygen concentrators used by patients inthe home care setting where cost and frequency of maintenance performedby a technician should be minimized.

The application of oxygen concentrators for therapeutic use is known,and many variants of such devices exist. A particularly useful class ofoxygen concentrators is designed to be portable, allowing users to moveabout and to travel for extended periods of time without the need tocarry a supply of stored oxygen or to have any maintenance performed ontheir equipment. These portable oxygen concentrators are typically inthe range of 2 to 20 lbs and produce from 0.3 to 5.0 LPM of oxygen. Mostof these portable concentrators are based on Pressure Swing Adsorption(PSA), Vacuum Pressure Swing Adsorption (VPSA), or Vacuum SwingAdsorption (VSA) designs which feed compressed air to selectiveadsorption beds. In a typical oxygen concentrator, the beds utilize azeolite adsorbent to selectively adsorb nitrogen, resulting inpressurized, oxygen-rich product gas.

The main elements in a typical portable therapeutic oxygen concentratorare shown in FIG. 1. Air is drawn in, and typically filtered, at airinlet 1 before being pressurized by compressor 2 to a pressure of 1.2 to2.5 atmospheres. The pressurized air is directed by a valve arrangementthrough adsorbent beds 3. An exemplary adsorbent bed implementation,used in a concentrator design developed by the inventors, is two columnsfilled with a lithium exchanged zeolite adsorbent in the ratio of about1 gram of adsorbent per 1-10 ml of oxygen produced. The pressurized airis directed through these adsorber vessels or columns in a series ofsteps which constitute a gas separation cycle, often a PSA cycle or somevariation including vacuum instead of, or in conjunction with,compression yielding overall compression ratios of about 1.5:1 to 4.0:1.Although many different arrangements of adsorber vessels and gasseparation cycles are possible, the result is that nitrogen is removedby the adsorbent material, and the resulting oxygen rich gas is routedto a product gas storage device at 4. Some of the oxygen product gas canbe routed back through the bed to flush out (purge) the adsorbednitrogen to an exhaust 6. Generally multiple adsorbent beds, or columnsin the exemplary device, are used so at least one bed may be used tomake product while at least one other bed is being purged, ensuring acontinuous flow of product gas. The purged gas is exhausted from theconcentrator at the exhaust 6.

Such gas separation systems are known in the art, and it is appreciatedthat the gas flow control through the compressor and the adsorbent bedsis complex and requires precise timing and control of parameters such aspressure, flow rate, and temperature to attain the desired oxygenconcentration of 80% to 95% purity in the product gas stream.Accordingly, most modern concentrators also have a programmablecontroller 5, typically a microprocessor, to monitor and control thevarious operating parameters of the gas separation cycle. In particular,the controller controls the timing and operation of the various valvesused to cycle the beds through feed, purge, and pressure equalizationsteps which make up the gas separation cycle. Also present in mostportable concentrators is a conserver 7 which acts to ensure that oxygenrich gas is only delivered to a patient during inhalation. Thus, lessproduct gas is delivered than by means of a continuous flow arrangement,thereby allowing for smaller, lighter concentrator designs. A pulse ofoxygen rich air, called a bolus, is delivered in response to a detectedbreath via the conserver. Using a conserver in conjunction with a gasconcentrator may reduce the amount of oxygen required to maintainpatient oxygen saturation by a factor of about 2:1 to 9:1. A typicalconcentrator will also contain a user/data interface 8 includingelements such as an LCD display, alarm LEDs, audible buzzers, andcontrol buttons. In addition to the above subsystems, most portableoxygen concentrators contain a rechargeable battery and charging systemto power the concentrator while away from an AC or DC power source.These battery systems are typically composed of lithium ion cells andcan power the concentrator from 2-12 hours depending on the amount ofoxygen required by the patient, device efficiency, and the capacity ofthe battery pack which may range from about 40 Watt-hours to 250Watt-hours on systems with multiple battery packs.

To be practical and usable by an individual needing therapeutic oxygen,portable oxygen concentrators should be less than about 2100 cubicinches and preferably less than 600 cubic inches in total volume, lessthan about 20 pounds and preferably less than 8 pounds in weight, andproduce less than about 45 decibels of audible noise, while retainingthe capacity to produce a flow of product gas adequate to provide for apatient's oxygen needs, usually a flow rate prescribed by a medicalpractitioner in about the range of 1 LPM to 6 LPM. Further, a portablemedical oxygen concentrator must work under varied environmentalconditions such as 0° C. to 40° C. and 0%-95% relative humidity withoutcostly or frequent service or maintenance requirements. Although fixedsite PSA based concentrators have been available for many years, suchfixed site units may weigh 30-50 pounds or more, be several cubic feetin volume, and produce sound levels greater than 45 dBA. Thus portableconcentrators involve a significant amount of miniaturization, leadingto smaller, more complex designs compared to stationary units. Systemsize, weight, and complexity may lead to fewer mitigative options ordesign choices against contamination and other wear and tear effectsthat can lead to an unacceptably short maintenance interval.

One particular challenge of portable concentrator design is that theadsorbent beds must by necessity be small, yet capable of producing anadequate quantity of product gas. A portable oxygen concentrator mightrequire oxygen production of greater than 3 ml of oxygen per gram ofadsorbent in order to achieve an acceptable size of less than 600 cubicinches. Since the adsorbent beds are optimized for O₂ production pergram of adsorbent, any significant decrease in capacity of the beds overtime can result in decreased product purity as the required O₂production per gram of active adsorbent exceeds the limits of theadsorbent and PSA cycle operating parameters. One contributing factorthat can lead to a decrease in bed capacity is the adsorption ofimpurities that do not completely desorb during normal processoperation, leading to the accumulation and retention of impurities inthe beds and therefore less active adsorbent than originally intended inthe design. An example of such an impurity that reduces the adsorptioncapacity of many zeolites used in air separation is water. Somestationary concentrators utilize some means of removing water from thecompressed gas before feeding the adsorbent beds, but most rely on anexcess quantity of adsorbent to allow for contamination over time.Portable concentrators, by the nature of their application, are morelikely to be exposed to a wide range of operating conditions includinghigh humidity environments and/or rapid temperature changes that couldresult in the need for more frequent zeolite replacement. If water ispresent, either in the form of liquid (condensed out of the feedstream)or vapor, and enters the molecular sieve beds, the beds willirreversibly adsorb at least some of this water during each adsorptioncycle. The energy of adsorption of water on lithium exchanged zeolitesused in air separation is very high and not all water adsorbed duringthe adsorption steps in the process is desorbed during evacuation/purgeof the beds under typical PSA cycle operating parameters. Therefore,complete removal of adsorbed water from zeolite beds usually entailsapplying some sort of energy to the beds, such as thermal, infrared, ormicrowave, and purging with a dry gas or applying a vacuum to the bedsduring the regeneration process. These regeneration processes areimpractical in a portable concentrator due to high temperature or highpower requirements. As a result, the accumulation of adsorbed water overtime results in a reduction in capacity of the beds, as fewer sites areavailable for nitrogen binding. Fewer binding sites in the adsorbent bedcan result in a decrease in product purity over time as nitrogen passesthrough the sieve beds and dilutes the oxygen product gas, and shortensthe service life of the concentrator. Many zeolites used in airseparation, and in particular advanced adsorbents, particularly the highlithium containing low silica X type zeolite (LiLSX) used in portableconcentrators, are hydrophilic in their activated state due to theinteraction of the strong dipole moment of water molecules with theelectric fields present in the LiLSX cages and can therefore be prone tothis problem. In the effort to make more compact and efficientconcentrators, PSA cycle frequencies can increase to rates approaching10 cycles per minute and adsorbent productivity increases accordinglywith advances in process and adsorbent technology to productivitiesexceeding 10.0 ml of oxygen per gram of adsorbent. The correspondingdecrease in adsorbent inventory exacerbates the problem as the amount ofgas processed per unit of adsorbent increases proportionally, (the bedsize factor decreases) and the presence of impurities in the process gascan deactivate the adsorbents at a much faster rate than withconventional PSA processes, as described in U.S. Pat. Nos. 7,037,358 and7,160,367, which are incorporated by reference herein.

It is therefore necessary to design portable oxygen concentrators suchthat zeolite contamination can be prevented or handled in a manner thatavoids costly or frequent maintenance by a field technician or equipmentprovider. While the inventors have previously disclosed a system thatachieves long sieve bed life by removing water prior to the feed gascontacting the zeolite in U.S. co-pending application Ser. No.11/998,389, whose teachings are incorporated by reference, this approachadds size and cost to the system to achieve its resistance to zeolitecontamination. It is therefore desirable to design a portable oxygenconcentrator that minimizes size and weight as a function of oxygenoutput with commonly available commercial adsorbents such as Z12-07©manufactured by Zeochem or OXYSIV MDX© manufactured by UOP. Whileeliminating water removal components such as membrane air dryers orpretreatment layers such as activated alumina or an NaX type zeolitewill reduce the size and weight of the sieve beds it will also reducethe service life of the sieve beds to an unacceptable level. Oxygenequipment used for Long Term Oxygen Therapy (LTOT) is optimally deployedfor 3-5 years without any service requirements. Any service requirementwithin that time interval simply adds to the overall cost of theequipment, which substantially reverses any cost benefit gained byremoving a membrane air dryer or pretreatment layer. Further, allowingsieve bed contamination without prevention or service may lead toproviding 82-87% purity oxygen instead of 87-95% pure oxygen to thepatient. At this time, portable oxygen concentrator adoption willrequire smaller, lighter devices that do not require field service by atechnician or equipment provider, but also minimize size and cost of theequipment.

A typical adsorbent bed or adsorber is constructed of a column with aninlet port and an outlet port arranged at opposite ends. The inlet portis used for admitting pressurized feed gas from the compressor as wellas exhausting the waste gas out of the system in the countercurrent(opposite to the direction of flow of the feed gas) direction. Theoutlet port allows product gas to flow to the accumulator where it canbe delivered to the patient. The outlet port also admits product gasback into the exhausted sieve bed in the countercurrent direction topurge the column of remaining waste gas prior to introducing additionalfeed gas. Inlet and outlet ports must create a sealed connection toallow pressurized feed gas and product gas to pass into and out of thecolumns without wasteful leaks that would upset the balance of thesystem or let oxygen rich product gas escape from the system. The inletand outlet port connections are typically composed of barb fittings,quick connect fittings, tapered pipe thread fittings, or integratedmanifold connections such as adhesives, face seals, gaskets, o-rings orstraight threads. The adsorbers would typically be connected to thevalve manifold of the concentrator through tubing or a direct manifoldconnection. Either prior art construction method resulted in a robustpneumatic connection that was only meant to be disconnected by a trainedservice technician who could access the internal components of theconcentrator and disconnect or disassemble the inlet and outletconnections. Some columns, such as those that are adhesive bonded to anintegrated manifold, may not be removable at all in a field serviceenvironment and must be replaced in combination with other systemcomponents to achieve zeolite replacement.

BRIEF SUMMARY OF THE INVENTION

The invention is a portable oxygen concentrator platform, including aPSA/VPSA/VSA core section capable of mating with user replaceableadsorbers. The core section includes all of the concentratorinstrumentation, mechanics, and pneumatics other than the adsorbers andincludes a housing; a controller; a user interface; at least onecompressor, air control valve, and air filter, comprising a PSA/VPSA/VSAoxygen system when mated with user replaceable adsorbers; and a patientdelivery apparatus. The core also includes at least one adsorberreceptacle that is capable of mating to a user replaceable adsorber. Thereceptacle includes at least two pressure sealed gas connections toinlet and outlet ports of the core section, at least two easilydisconnectable pressure sealed gas connectors for mating to an inlet andoutlet port on a user replaceable adsorber, and a user operable adsorberretention mechanism. Mating a user replaceable adsorber with theadsorber receptacle forms a complete portable oxygen concentrator. Theinvention is applicable to the portable medical concentrator field wherethe concentrator preferably weighs less than 10 pounds, produces lessthan 45 dba acoustic noise when operating, and has an output gas flow of5 lpm or less and has rechargeable battery capable of running theconcentrator for greater than 2 hours. In a preferred embodiment, theconcentrator weighs less than about 8 pounds.

The invention also may be a combination of the platform section and atleast one User replaceable adsorber, forming a complete portableconcentrator. The user replaceable adsorber capable of mating withcompatible portable oxygen concentrator platform includes at least oneselective adsorbent, disconnectable pressure sealed gas connectors formating to the platform receptacle inlet and outlet connectors, andmating retention mechanism to the platform adsorber receptacle retentionmechanism.

In certain embodiments, the battery mounts to the instrumentationsection and prevents removal of the adsorbers while the battery isattached, and there may be a removable case that encloses the platform,user replaceable adsorber beds and battery when all three are mountedtogether.

In other embodiments the inlet and outlet ports may include one or moreradial seals, and the adsorber and receptacle ports insert beyond theradial seal by at least 0.030″. The leak rate of the seals is preferablyless than about 10 SCCM at the maximum rated operating pressure orvacuum level of the adsorber which may be from 0.2 atmospheres to 3.0atmospheres. In certain embodiments the adsorber ports are coaxial withthe receptacle ports.

In some embodiments either the platform or adsorber retention mechanismcomprises a sliding spring loaded plunger and the corresponding matingretention mechanism includes a slot which mates with the plunger. Thespring loaded plunger snaps into the slot when the adsorber is mated tothe platform thereby retaining the adsorber and actuation of the plungerreleases the adsorber. The retention force of the release mechanism ispreferably less than about three pounds, and the plunger may be fingeractuated to release the adsorber.

In other embodiments, either the platform or adsorber retentionmechanism includes a screw operated tab and the corresponding matingretention mechanism includes a slot which mates with the tab. The tab isrotated into the slot when the adsorber is mated to the platform therebyretaining the adsorber and reverse rotation of the tab releases theadsorber.

In other embodiments, the platform retention mechanism includes a pushbutton actuated spring loaded plunger and the adsorber retention matinghardware includes a slot which mates with the plunger. The spring loadedplunger snaps into the slot when the adsorber is mated to the platformthereby retaining the adsorber and push button actuation of the plungerreleases the adsorber. The adsorber is preferably released with lessthan about 25 Newtons of force applied to the push button, and theremovable adsorber mates to the instrument section in an axisperpendicular to the flow of gas through the column.

In preferred embodiments, the adsorber receptacle gas connections areconnected to the air control valves by compliant pressure members. In aparticular version, the adsorber receptacle gas connectors are directlyconnected to the compliant members, and when connected to the compliantmembers, are held in place by a housing mounting element structurallyindependent from the receptacle gas connector. In an alternativeembodiment at least one of the gas connection could be directly to amanifold.

In other embodiments, the platform retention mechanism includes athreaded adsorber and threaded adsorber receptacle. The inlet and outletports may be coaxial and located on one end of the adsorber. Theadsorber or the adsorber receptacle have radial seals that enable thesealing of the gas connection in any rotational orientation around thecenter axis of the adsorber.

In certain embodiments, the adosrber is retained to the receptacle by atwist to lock mechanism. The twist lock may be engaged by less thanabout 180 degrees of rotation, and the inlet and outlet ports may becoaxial and located on one end of the adsorber.

In other embodiments, the platform retention mechanism includes a hingedcover. The hinged cover snaps into place when the adsorber is mated tothe platform thereby retaining the adsorber, and opening the coverreleases the adsorber. The hinged cover may preferably be disengagedwith less than about 25 Newtons of force and can be operated by afinger.

In other embodiments, one of the inlet or outlet ports is rigidlymounted to the receptacle by any of a twist to lock or threadedengagement and at least one of the inlet of outlet port connections ismade by attaching a flexible tube to the port.

BRIEF DESCRIPTION OF THE DRAWINGS

The understanding of the following detailed description of certainpreferred embodiments of the invention will be facilitated by referringto the accompanying figures.

FIG. 1 shows the general elements of gas concentrators as applicable tocertain embodiments of the invention.

FIG. 2 illustrates the general concept where the concentrator platformis one portion and the user replaceable adsorber is another portion of acomplete concentrator.

FIG. 3 illustrates the concentrator sections in both an unassembled andassembled state.

FIG. 4 illustrates an assembled concentrator in a case.

FIG. 5 depicts an exemplary user replaceable adsorber.

FIG. 6 depicts one example of a suitable user actuatable adsorberretention mechanism.

FIG. 7 depicts another example of a suitable user actuatable adsorberretention mechanism.

FIG. 8 depicts a port seal for a replaceable adsorber where the port isindependently mounted from the platform chassis.

FIG. 9 depicts another example of a suitable user actuatable adsorberretention mechanism.

FIG. 10 depicts an alternative port geometry.

FIG. 11 depicts an arrangement where user replaceable adsorbers areinstalled with a threaded interface.

FIG. 12 depicts details of the threaded interface.

FIG. 13 depicts a twist-lock adsorber interface.

FIG. 14 depicts another example of a suitable user actuatable adsorberretention mechanism.

FIG. 15 depicts another example of a suitable user actuatable adsorberretention mechanism.

FIG. 16 shows that alternative inlet and outlet port arrangements arepossible.

FIG. 17 depicts a variety of radial seal arrangements.

FIG. 18 shows an embodiment where one or more of the gas connections maybe directly to a manifold

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, general features of a portable therapeutic gasconcentrator are shown. Typically gas is drawn into the inlet through aninlet filter 1 into a compressor 2. Compressed air is then delivered ata rate of about 3 LPM to 30 LPM (through various filters and otherdevices) to a gas separation section for selectively adsorbing acomponent of the gas. The preferred embodiments of the invention,although applicable to a variety of gas concentrator implementations,will be described in detail for the case where the inlet gas is air, andthe gas separation section is based on PSA, VSA, VPSA or somecombination thereof, utilizing adsorbent beds 3 which selectively adsorbnitrogen, producing oxygen rich product.

A variety of gas separation section cycle types and bed arrangements areknown in the art, most of which can benefit from the embodiments of theinvention. Whatever the details of the gas separation section 3,typically product gas is accumulated in a storage device 4. Storagedevices may include a tank in the traditional sense, or may be someother device effective for holding a volume of gas, such as a tube, orsome other volume filled with an adsorbent to increase its holdingcapacity or even an empty portion of the adsorber itself at the productend of the adsorber. Many modern concentrators used for therapeuticapplications also include a programmable controller 5 to operate theconcentrator and provide for user interface 8 and communications. Alsotypical are gas exhaust 6, which may have a vacuum applied in the caseof VPSA or VSA systems, and delivery to patient, which often is througha conserver device 7.

Despite the effective moisture mitigative measures described inco-pending application Ser. No. 11/998,389 which might remove 40-98% ofwater molecules from the feed gas stream, some moisture will remain inthe beds 3 when the concentrator is turned off. For the case where thereis a desiccant layer, even for a very dry design, the desiccant existsto remove any remaining water as well as other impurities, such as CO₂,from the feed gas. During operation impurities are not a significantproblem, as the bed 3 is back-purged or evacuated with vacuumperiodically in the Adsorption Cycle, thereby not leaving time formoisture and other impurities to diffuse into the adsorbent. When theconcentrator is not running, particularly for a long period of time,there will be a strong driving force to diffuse for any impuritiesadsorbed on the pretreatment layer (or feed end of the bed in the caseof no pretreatment layer used) or in the gas phase in the void space ofthe desiccant/adsorbent at the feed end of the bed. If the concentratoris not sealed to the outer atmosphere via a valve on the exhaust,contaminants can diffuse either to the outer atmosphere (likewise othercontaminants can diffuse into the beds) or the contaminants can diffuseinto the active “clean” section of the bed(s). If the concentrator issealed to the outer atmosphere via a valve, any impurities present willdiffuse into the bed only. Pretreatment layers are often selected due totheir ease of regeneration during process cycles relative to that forthe contaminants in the active separation layer. Thus during shutdownconditions the result can be a material with a low affinity for a givencontaminant adjacent to a material with a high affinity for a givencontaminant, and a large gradient in chemical potential for thecontaminant provided sufficient treatment of the feed gas has takenplace. Given the complex array of components required to prevent thecontamination of zeolite while a portable oxygen concentrator is runningand while it is in storage, the inventors devised a way to treat thesieve beds as a semi-disposable item so that they can be readilyreplaced rather than protected or overdesigned to achieve the requireddevice service life of the system as a whole.

While it is known in the art to make the zeolite beds easily serviced,there have been no successful designs that minimize the number ofreplacement components and simultaneously retain the ability for thepatient to easily change the sieve beds. The invention herein requires aconcentrator to be designed from the ground up around the concept of afield replaceable sieve bed. The sieve beds must be easily removed fromthe system, yet still retain their air-tight sealing mechanisms androbust resistance to shock, drop, and vibration. In medical oxygenconcentrators, and particularly portable oxygen concentrators currentlyin the marketplace, access to the sieve beds typically requires removalof several outer housing components, tubing connections, fittings,screws, and other hardware components. These designs are simplyunsuitable for field service by the user of the oxygen concentrator.

A particularly effective embodiment of the invention is a portableoxygen concentrator where the sieve bed cartridges or adsorbers can beremoved and replaced without removing the outer housing or any fastenersof any kind. FIG. 2 illustrates a preferred embodiment where inlet andoutlet gas connections 201 and 202 are located externally to aconcentrator platform section 20, containing the concentrator elementsother than the adsorber beds, to allow for easy field replacement ofadsorber 21 with inlet and outlet ports 211 and 212 respectively.Further, the adsorbers are robustly attached to core platform 20 towithstand the necessary shock, vibration, and impact a portable oxygenconcentrator may endure via retention mechanism components 203 and 213.By locating the adsorbers 21 outside of the platform 20, the integrityof the concentrator assembly 20 is not compromised by being accessed bythe user who would not have adequate training to perform maintenance oninternal components of the platform 20. The receptacle ports 201 and 202are preferably connected to the air valves by compliant members 9 and10.

A portable concentrator with sieve beds designed for field service issubstantially different than a typical portable oxygen concentrator. Thedesign for patient service changes the layout of the concentrator sothat operational components of the system are accessible to the patientby being located external to the concentrator housing. While this changefacilitates the patient servicing of the system, it also poses aestheticchallenges to the designer since the portable concentrator is usedoutside the home and must not look out of place while being carried by apatient. Therefore, it is an objective of the present invention toseamlessly integrate the adsorbers into the industrial design of theconcentrator so that they remain accessible, but appear to blend in withthe overall design of the concentrator. In a preferred embodiment shownin FIG. 3 the adsorbers 21 form the sides of the concentrator while thebattery 31 forms the bottom of the concentrator. FIG. 3 further depictsa mechanical advantage designed by the inventors to use the mechanicallyrobust battery 31 and battery latching mechanism 310 to reinforce theretention of the adsorbers and to prevent inadvertent release of theadsorbers during operation. To remove the adsorbers 21 for the purposeof exchanging them, the user would first remove the battery to accessthe adsorber release mechanisms 203/213. The entire system 30 is thenpreferably mounted inside a carrying case 40 to enable portable use bythe user (FIG. 4).

FIG. 5 depicts a preferred embodiment of the adsorber designed by theinventors. The adsorber is built as an independent unit and can bepneumatically interfaced to the platform 20 via inlet and outlet ports211 and 212 while being mechanically interfaced to the concentrator viaretention receptacle 214. The internal components of the adsorber 21 aresimilar to other adsorbers found in portable oxygen concentratorsdesigned by the inventors. The adsorbers contain a nitrogen selectiveadsorbent 214, porous frits 21 d to retain the adsorbent and springs 21c to prevent the adsorbent from moving and breaking down during pressurecycling that is typical with a PSA system. The preferred embodiment 21shows the column cap 21 b being threaded into the column 21. Thisembodiment allows the external surfaces of the adsorber to be smooth andfree of fasteners or retainers that would otherwise pose a hazard to theuser while exchanging the adsorbers in the concentrator. Further, thethreaded engagement of the cap to the column ensures that thecontaminated adsorbers can be returned to the factory for replacement ofthe adsorbent, thus further reducing the cost of the adsorber exchange.The cap could alternatively be permanently affixed to the column byrolling the edge of the column over the cap for retention or usingadhesive to seal the two parts together, but these methods make theadsorber a throw-away item which creates waste. The preferred embodimentdesigned by the inventors allows only the adsorbent or adsorbents to bediscarded during an adsorber refurbishment at the factory.

A further objective of the inventors was to develop an appropriatelatching mechanism that would securely hold the adsorbent vessels sealedto the concentrator, but also allow for easy replacement by the patient.FIG. 6 depicts an exemplary latching mechanism comprised of a receptacle214 on the adsorber and a retention plunger 204 on the platform 20. Thelatching plunger 204 is held in place by spring force applied by spring204 a. The latch is disengaged by the user by sliding the engagementbutton 204 b away from the column latch receptacle 214. The forceapplied by spring 204 a must be sufficient to prevent inadvertentdisengagement of the latch, but also low enough to be easily disengagedby the users finger without a painful or difficult effort on the part ofthe user. The inventors have found that a disengagement force ofapproximately 10-25 Newtons meets both of these requirements. As shownin the Figure, the location of the mechanisms could be switched betweenthe adsorber and platform, but it is generally preferable to keep thecost and complexity as low as possible for the replaceable adsorber, sothe latching hardware on the platform is preferable.

FIG. 7 depicts an alternative embodiment of the invention where theretainer 216 is engaged by locking tab 215 via the rotation of lockingscrew or knob 206. Reverse rotation of the locking screw or knob 206disengages the locking tab 215 allowing the adsorber to be removed. Thisdesign includes the advantage of not requiring a spring to maintain theretention of the adsorber, but the rotational design also may require acommon tool such as a Phillips screwdriver or Torx driver to remove orinstall the adsorbers. Requiring a tool for removal or installation ofthe adsorbers might be an advantage in some usage scenarios or adisadvantage in other usage scenarios. The inventors designed theconcentrator system to allow for these differing usage scenarios so thatthe optimal latching and retention mechanisms may be chosen accordingly.As for the embodiment of FIG. 6, the placement of the mechanisms couldbe reversed as shown, but the placement of the rotating tab on theplatform is preferable.

As in any manufacturing operation, there will be variations in thedimensions of all components of the system, so the user replaceableadsorbent must contain a significant amount of sealing overlap toprevent inadvertent leakage that would degrade the system's performance.Referring to FIG. 8, in a particular embodiment, the inlet and outletconnections 211 and 212 must therefore contain overlapping sealingelements that allow for some positional compliance without sacrificingthe quality of the sealing of the pneumatic connections. This compliantsealing mechanism is achieved by using an o-ring on the adsorber and avertical bore 201 a on the receptacle 201 that creates a seal along itsentire length, thus allowing between 1 and 5 millimeters of verticalcompliance to the seal. This compliance allows for some variation andcompliance in the latch as well as some variation in the height of thecolumn components that would be seen in a typical manufacturedcomponent. Further, FIG. 8 depicts the gas receptacle 201 as a modularcomponent that is independent of the platform 20. This is accomplishedby connecting adsorber receptacle port 201 directly to compliant member9, with a locking mechanism 201 b. Thus platform 20 is used to locatethe port 201, but they are not a shared structure. By decoupling thepneumatics from the structural elements of the system, the pneumaticsare protected from the adverse affects of drop or impact. In the extremecase when platform 20 housing components are broken during impact ordrop, port 201 may likely stay connected to member 9 and column inlet oroutlet fitting 212 a. Thus the pneumatic system integrity may bemaintained by adhering to the modular gas connector system 201 and 212as shown in FIG. 8 even in the event of damage to the core system 20.

FIG. 9 depicts an alternate latching mechanism that utilizes push buttonadsorber release buttons 207 to disengage the latching mechanism 207 band 207 c and release the adsorbers 21. Again, the spring 207 a mustexert an optimal force of about 10 to 25 Newtons on the latchingmechanism to sufficiently secure the adsorber 21 during use and pressurecycling while still enabling the finger of the user to overcome thespring force and release the adsorber 21 without discomfort ordifficulty.

FIG. 10 depicts another alternate embodiment of the invention where theaxis of insertion of the inlet and outlet ports 211 and 212 areperpendicular to the axis of flow of gas through the adsorber 21. Thisembodiment simplifies the design by utilizing the same gas connectionsat the inlet and the outlet port, but does not have the advantage ofbeing able to utilize the battery as a redundant retention mechanismduring use.

The coaxial threaded adsorbers 21 in FIGS. 11 and 12 are anotherembodiment of the invention where both gas inlet and gas outlet ports211 and 212 are coaxial and located at the same end of the adsorber byutilizing an integral return tube to retrieve gas from the opposite endof the column. The engagement and retention threads 217 create themechanically robust connection between adsorber 21 and platform 20 whilethe pneumatic connections 211 and 212 are radially sealed by o-ringswith sufficient vertical overlap to allow adsorber 21 to seal in anyrotational orientation such that rotational position or timing isindependent from the sealing. Adsorber endcap 21 a is threaded ontoreturn tube connection 212 to seal the return tube. Adsorber endcap isthen sealed to column 21 c in any rotation by any number of possiblesealing methods such as an o-ring or face seal gasket. The entireadsorber including column 21 c and endcap 21 a then mate to core section20 to form a complete portable oxygen concentrator. The rotationalindependence ensures that user replacement of the adsorber and thevariable tightening torque applied by the user will not createdetrimental leaks at the inlet and outlet gas connections.

The alternate embodiment of the invention depicted in FIG. 13 utilizes atwist-lock mechanism to lock the adsorber 21 to the platform 20.Progressively engaging locking tab 218 draws adsorber 21 into thereceptacle located in platform 20 and is ideally employed in combinationwith the coaxial adsorber design where both inlet and outlet ports 211and 212 are collocated at a single end of the adsorber. Alternatively,one of the inlet or outlet ports may be located at the opposing end ofthe adsorber 21 and the gas connection may be made with a flexibletubing element 10 as depicted in FIG. 15

Yet another alternate embodiment of the user replaceable adsorber isdepicted in FIG. 14. In this embodiment, adsorber 21 is held in place toplatform 20 by a hinged floorplate 209 such that no retention elementsat all are required on the adsorber 21. In this embodiment the hinge 209a and the latch 209 b are both mounted on the platform 20 such thatfloorplate prevents the adsorber from disengaging from the platform 20when latched in the closed position by latch 209 b.

The specific definition of the inlet and outlet ports on adsorber 21 aremerely chosen by convention and can be reversed in any embodiment asdepicted in FIG. 16. A typical adsorber as designed by the inventorsutilizes a larger inlet port where feed gas enters the column to preventpower losses caused by flow restriction and a smaller port on theproduct end or outlet where the oxygen exits the adsorber or enters theadsorber during the purge step of the PSA cycle. In constructing theadsorber, the feed or inlet end of the adsorber may be further definedwhen a layered adsorbent system is utilized and a pretreatment layer isused to remove contaminants from the feed stream prior to the exposingthe main layer adsorbent to the feed stream.

Inlet and outlet ports and receptacles 201 and 211 may utilize a varietyof well established sealing elements as depicted in FIGS. 17a and 17b .Sealing element 17 is ideally a compliant o-ring made from one ofseveral compounds such as rubber, viton, or silicone. Alternately, thesealing element 17 may be a custom face sealing gasket also made ofrubber, viton, or silicone, but this embodiment may lack the necessarycompliance to produce a repeatable and robust seal as part tolerancesvary in a high volume production environment.

Although the preferred approach to connect the adsorber/receptacle portsto the platform internal valving is by compliant member for increasedresistance to shock, it is certainly possible to make one or more theseconnections by having the receptacle ports connect directly to amanifold. Such an arrangement is shown by way of example where one portof adsorber 21 connects directly to manifold 181.

The foregoing description of the preferred embodiments of the presentinvention has shown, described and pointed out the fundamental novelfeatures of the invention. It will be understood that various omissions,substitutions, and changes in the form of the detail of the apparatus asillustrated as well as the uses thereof, may be made by those skilled inthe art, without departing from the spirit of the invention.Consequently, the scope of the invention should not be limited to theforegoing discussions, but should be defined by appended claims.

We claim:
 1. A portable oxygen concentrator, comprising: a platform,comprising: a housing, a controller, a user interface, at least onecompressor, air control valve, and air filter, a patient deliveryapparatus, at least one adsorber receptacle comprising two gas connectorports and at least one adsorber retention element wherein the gasconnector ports are separated by a lateral distance; and at least oneseparable user replaceable adsorber comprising: a column having a topend and a bottom end, the column configured to contain a nitrogenselective adsorbent material, at least one retention element on thecolumn configured to mate directly with the adsorber receptacleretention element and, a first and a second disconnectable pressuresealed gas connector disposed on the top and bottom ends of the columnrespectively, said first and second gas connectors each comprising adistal end, a proximal end, and a channel extending therebetween,wherein the distal ends are configured to mate with the gas connectorports on the platform and the proximal ends are attached to the column,wherein the gas connectors are in fluid communication with the columnand arranged in a manner such that the distal ends of the gas connectorsextend outwardly in the same direction and the central axes of the gasconnectors are substantially parallel to each other and laterally offsetby a distance that corresponds to the lateral distance separating thetwo gas connector ports, wherein; the adsorbers are configured to matewith the platform to form a complete oxygen concentrator; the adsorberswhen mated are accessible from the exterior of the platform; theretention mechanism is accessible on the exterior of the platform, andwhen the retention mechanism is engaged the gas connections between theplatform and the top and bottom surface gas connectors of the column aremade directly; at least one of the adsorber or the adsorber receptacleretention mechanisms are hand operable; wherein; the concentrator weighsless than 10 pounds, produces less than 45 decibels acoustic noise whenoperating, and has an output gas flow of 5 liters per minute or less andhas a rechargeable battery capable of running the concentrator forgreater than 2 hours.
 2. The portable oxygen concentrator of claim 1wherein the concentrator weighs less than about 8 pounds.
 3. Theportable oxygen concentrator of claim 1 wherein the inlet and outletports for mating with a user replaceable adsorber are disposed so thatthe inlet and outlet ports are coaxial to the flow through the adsorberand are open to the inlet and outlet ports of the adsorber.
 4. Theportable oxygen concentrator of claim 1 wherein at least one of theinlet or outlet connectors insert beyond an adsorber radial seal by atleast 0.030 inches.
 5. The portable oxygen concentrator of claim 1wherein the inlet and outlet ports contain at least one radial seal. 6.The portable oxygen concentrator of claim 1 wherein the leak rate of thegas connectors is less than about 10 Standard Cubic Centimeters perMinute at the maximum rated operating pressure of the adsorber.
 7. Theportable oxygen concentrator of claim 1 wherein the adsorber receptaclegas connectors are connected to the air control valve by compliantpressure members.
 8. The concentrator of claim 7 wherein the adsorberreceptacle gas connectors are directly connected to the compliantmembers, and when connected to the compliant members are held in placeby a housing mounting element structurally independent from thereceptacle gas connector.
 9. The portable oxygen concentrator of claim 1wherein the adsorber retention mechanisms comprises a sliding springloaded plunger and the corresponding retention mating hardware comprisesa receptacle which mates with the spring loaded plunger, wherein thespring loaded plunger snaps into the receptacle when the adsorber ismated to the adsorber receptacle thereby retaining the adsorber andactuation of the spring loaded plunger releases the adsorber.
 10. Theconcentrator in claim 9 wherein the actuation force of the spring loadedplunger is less than about 25 Newtons.
 11. The concentrator of claim 9wherein the spring loaded plunger is finger actuated to release theadsorber.
 12. The portable oxygen concentrator of claim 1 wherein atleast one of the adsorber receptacle gas connectors are directlyconnected to the air control valves on a manifold.
 13. The portableoxygen concentrator of claim 1 wherein the gas connectors are sealed byo-ring seals.
 14. The concentrator of claim 1 wherein each adsorber bedis individually releasable.